The Local Area Network (LAN) was developed in response to the needs of computer users to communicate among themselves and to share computing resources such as printers, file servers and electronic mail systems. The Institute of Electrical and Electronic Engineers (IEEE) defines a LAN as a network system that "allows a number of independent devices to communicate directly with each other, within a moderately sized geographic area over a physical communications channel of moderate data rates." Typically, LANs are implemented within buildings or among buildings in a campus environment. Devices on a LAN are usually directly connected to a dedicated cable or other medium.
With numerous devices connected to a dedicated medium, some means of controlling access to the medium is required so that any two devices wishing to exchange data can do so when required. One of the most common media access control protocols is carrier-sense multiple access with collision avoidance (CSMA/CD) developed for and typically used on a bus/tree LAN topology. CSMA/CD is fully described in the IEEE 802.3 standard. The most common implementation of LANs using CSMA/CD is Ethernet, developed by Xerox Corporation.
In CSMA/CD, a device first listens to the channel, referred to as carrier-sensing, to determine if another device is transmitting data. If the channel is busy, the device will wait a certain amount of time and check the channel again. If the channel is free, the device will begin transmitting. If two devices desiring access to the channel both begin transmitting at the same time, a collision will occur. Upon sensing a collision, the transmitting devices will apply a signal to the channel indicating that a collision has occurred, and that all devices should ignore the current data frame. The transmitting devices will then each wait a certain amount of time and attempt to re-transmit.
Concurrent with the development of the LAN is the development of the wide area network (WAN). As its name implies, the primary distinguishing characteristic of a WAN over a LAN is its scope of geographic coverage. WANs are typically used to interconnect LANs that are sufficiently distant from one another to be beyond the physical transmission limitations of a LAN. This is analogous to our telephone network wherein local telephone systems are interconnected by long distance carriers. And, in fact, it is typical for WANs to utilize the public telephone network (PTN) facilities.
An increasingly popular application of LAN/WAN technology is internet and intranet access from work and home. This application is typically implemented over the PTN using point-to-point connections or over the public switched telephone network (PSTN) using dial-up or ISDN (Integrated Services Digital Network) modems to access an online service (OLS), which typically would be a company's restricted access intranet, or a Network Service Provider (NSP) who then provides access to the Internet. A problem with this typical implementation is the relatively low data transmission speed of these modems as compared to the transmission speed to the desktop that a user of a company LAN may see. High-speed dial-up modems currently operate in the 56 Kbps range, and ISDN currently operates in the 128 Kbps range, whereas a company LAN covering a campus environment could operate in the 10 Mbps-to-the-desktop range.
Another problem with this typical implementation is the use of limited central office switching resources. The longer average connect time for an "internet call" versus a regular telephone call will result in an increased requirement for central office switching resources as access to OLSs over the PSTN continues to grow.
A solution that overcomes the aforementioned problems that is gaining in popularity is to implement data networks using the existing PTN wireline network and twisted pair, and to bypass the central office switching equipment and use equipment specifically designed for data networking to transport data on these data networks. This data networking equipment, which is well known in the art, includes routers, concentrators and data switches. In essence, this solution extends the LAN/WAN to the home or business.
However, a problem with this solution is security of the transmissions from a subscriber's PC to the OLS. The typical Ethernet protocol is implemented as a broadcast protocol where all or a portion of all stations on a network monitor the transmission, and the targeted stations further process the transmission. Depending on the network topology, this may allow an enterprising individual to tap into the network and eavesdrop on the network traffic, obtaining, for example, various subscriber passwords. One current approach to ensuring the security of network transmissions is the use of data encryption. However, this approach can consume significant computing resources in carrying out the data encryption and decryption routines on the host and target systems. Another current approach is to implement the network in a full star topology of single-station nodes, with the central network controller device being a bridge, router or a hub with filtering or switching capabilities. However, these devices are designed more for interconnecting LANs and usually prove to be an expensive solution to address security issues in a star network.
Accordingly, it is an object of the present invention to provide a system and method that provides secure transmission of data between a subscriber and an OLS over a WAN.
Another object of the present invention is to provide a system and method that provides secure transmission of data between a subscriber and an OLS over a WAN that supports a known local area network protocol stack from media access control layer up to and including the transport layer.